The Commercial Mobile Alert System (CMAS) was established by the Federal Communications Commission (FCC) to allow wireless service providers to send emergency alerts to their subscribers. Such alerts are initially intended to be in the form of text messages, but may also take the form of audio and video alerts. The CMAS network will allow emergency services agencies, such as the Federal Emergency Management Agency (FEMA), to accept and aggregate alerts from federal, state, and local emergency operations centers, and send the alerts over a secure interface to wireless providers. The wireless providers can then distribute the alerts to their customers.
Emergency alerts issued by emergency services agencies may be intended to reach users in a specific geographical area. For instance, in the event of an impending potential natural disaster such as a hurricane, an emergency service agency may wish to notify the populations of the counties that have been determined to be most likely to be impacted by the potential disaster.
There are currently three types of emergency alerts. Presidential Alerts relate to national emergencies, Imminent Threat Alerts relate to emergencies where life or property is at risk, such as hurricanes or tornadoes, and Child Abduction Emergency/AMBER Alerts relate to missing or endangered children due to an abduction or runaway situation. Subscribers may be able to opt-out of receiving Imminent Threat and Child Abduction/AMBER alerts, but may not be permitted to opt-out of Presidential Alerts.